Feature [DEV-12022] Annotations that snap to data

[jayb]

Summary

This PR adds a "Snap to Data" mode for annotations that will keep an annotation pointing at a specific piece of data even when it moves around due to filter changes/etc.

Testing Steps

• Load this config
• Add an annotation, set it to "Snap to Data" mode
• When you toggle the filter on the chart, the annotation should move to follow the data
• If you attach the annotation to data that only exists in one view, it should disappear in the other view
• Experiment more with annotations in general and make sure they work as expected

[adamdoe]

Im seeing this example change the position between dev and feature/dev-12022-annotations:
http://localhost:8080/?config=/examples/feature/annotations/index.json&location=School